The Census of Marine Life (CoML) programme addresses three major questions: What lived in the oceans? What lives in the oceans now? What will live in the oceans? This 10-year programme (2000–2010) is a unique global effort to develop the first comprehensive assessment of life in the oceans, from bacteria to large animals, from coastal and shallow waters to the poorly known habitats in the deep sea, through more than 500 expeditions. It has resulted in partnerships and an international network of over 2700 scientists from 80 countries. Through 14 field studies in distinct ocean realms, ranging from analysing historical documents to modeling future ecosystems, the Census enables scientists to describe the diversity, distribution, and abundance of life in the oceans, to compare what once lived in the oceans to what lives there now, and to postulate what will live there in the future.

Many governments and organisations are supporting this unprecedented effort. The partnership between the Census, the Encyclopedia of Life, and the World Register of Marine Species has aggregated information on the 250,000 known marine species. Dedicated to the dissemination of knowledge, the Ocean Biogeographic Information System already provides the identification and location of nearly 120,000 marine species and reveals what we know so far – and what we do not know (probably more than 1 million species of pluricellular species and one billion different microbes remain undiscovered).

The Census has promoted synergetic approaches to assess and explain the diversity, distribution, and abundance of life in the oceans, focusing on domains where new approaches allowed discoveries and potentially new steps in science.

Exploring the continental margins – the ribbons of seafloor beginning at the edge of the continental slope and extending rapidly to abyssal plain depths

The continental margins of the deep oceans extend from the edge of the shelves at 200 m to the abyss below 4000 m and on tectonically active margins (e.g. near the Philippines) into the trenches to the greatest depths (11,190 m in the Philippine Trench). Habitats change quickly as the depth increases. Sunlit bottoms are replaced by darkness. Warmth is replaced by 2°C deep water. The amount of sun-based food reaching the bottom diminishes to a trickle, and the oxygen level at first drops then increases at greater depths. The familiar species of shallow water are replaced by unknown and mainly new species adapted to these conditions. Specialised ecosystems, discovered during the last decades, increase the uniqueness of margin animals when associated with chemically extreme habitats like methane-rich seeps, minimum-oxygen zones, reef-like coral mounds, and canyon outcrops. They were only recently studied owing to new and advanced technologies, in particular through the use of manned submersibles enabling unique and real-life experience due to the direct view of deep-sea life, the use of remotely operated vehicles and autonomous underwater vehicles. Acoustic technology is also used to obtain high-resolution seafloor topography maps. The combination of all these technologies has increased the scientific exploration capabilities. Investigations in different oceans have revealed the margins to be a wonderland of diverse habitats or hotspots of life, fundamental to the establishment of valuable fisheries, energy and mineral resources, and to the critical ecological service of carbon sequestration.

By creating an international network of more than 100 scientists who shared their knowledge from most continents, the project has confirmed that species changing with depth is a common feature throughout the world oceans. Although this zonation is a global pattern, each individual margin has locally distinct aspects, indicating the importance of local oceanographic conditions.

When exploring the local variation on margins, the scientists considered both the physical and the biological aspects of margin heterogeneity. The margins must now be seen as a dynamic series of habitats. Many deep rock bottoms support forests of deep-water corals (e.g. 400 km long along Mauritania). In the Gulf of Mexico, the Mediterranean, off Africa, off New Zealand, and probably in many places never explored, there are chemically extreme habitats. They are occupied by a unique biota, probably caused by a water layer very low in oxygen, by chemicals (methane, hydrogen sulfur) seeping from the seafloor, or by a combination of factors. This project has also made major contributions to the direct study of margin animals. Particular emphasis has been placed on more than 800 species of squat lobsters that inhabit the full range of margin habitats.

As we celebrate the success of the Census of Marine Life, the scientists have turned their attention to man’s increasing exploitation of an environment considered by many people just a few decades ago as too remote for detailed exploration.

We have fully discredited the idea that the margins are wastelands to be exploited without concern. Rather than fewer species, there are more. Rather than monotonous mud, there is a wealth of habitats, with more to be found.

For further information please contact the COMARGE.